1. Field of the Invention
The present invention relates to an optical disk apparatus for optically reproducing/recording a signal from/to an information carrier using an light beam from a light source such as a semiconductor laser. More particularly, the present invention relates to an optical disk apparatus for reproducing/recording a signal from/to a recordable disk having address sections which are wobbled about a track.
2. Description of the Related Art
An information carrier (optical disk) such as CD-AUDIO, CD-ROM, DVD-VIDEO and DVD-ROM contains information recorded thereon as concave/convex pits arranged along a single spiral track which spirally runs from the inner periphery of the disk to the outer periphery thereof.
In order to properly reproduce a signal on the track, a conventional optical disk apparatus typically performs the following control operations: a rotation control for rotating the optical disk at a predetermined number of revolutions: a focusing control such that the optical disk is irradiated with a light beam having a predetermined focused state; and a tracking control such that the light beam properly scans along the track of the optical disk.
Recent development in the high-density optical disk technology has seen the advent of a recordable optical disk xe2x80x9cDVD-RAMxe2x80x9d (digital versatile disk-random access memory).
Such a recordable DVD-RAM includes address sections as well as data sections where data can be recorded. Such a recordable optical disk is divided into a plurality of concentric zones which are successively arranged from the inner periphery of the optical disk to the outer periphery thereof. Each data section includes a guide groove (or a groove track) and a land track between two adjacent groove tracks.
FIG. 11 illustrates a portion of a recordable optical disk. Referring to FIG. 11, each data section includes a concave groove track 207 and a convex land track 206. A single pair of the groove track 207 and the land track 206 runs in a spiral pattern across the optical disk. An address section 205 is provided to interrupt the extent of the pair of the groove track 207 and the land track 206 along a boundary between the tracks 206 and 207. An actual beam spot on the optical disk is larger than the width of the track 206 or 207. Therefore, as the light beam moves along the groove track 206 or the land track 207, the beam can read an address in the address section 205 which is arranged along a boundary between the tracks 206 and 207.
An address 210, for example, is formed along a boundary between a track 209 and a track 202. Similarly, addresses 201 and 204 are formed respectively along a boundary between tracks 202 and 203 and along a boundary between tracks 203 and 208. Thus, a groove track and an adjacent land track share an address.
The track 202 is defined by the addresses 210 and 201. Similarly, the track 203 is defined by the addresses 201 and 204. These addresses are searched when recording data along a predetermined track or when reproducing the recorded data therefrom.
A spiral track formed by a string of pits (as in conventional CDs and DVD-ROMs) is not divided into zones. For such a spiral track, data is recorded from the inner periphery to the outer periphery at a constant linear velocity (i.e., at a constant recording density). In such a disk, as long as the CLV (constant linear velocity) control is properly performed, a PLL (phase locked loop) is pulled-in so that an address or data can successfully be reproduced.
In an optical disk such as a DVD-RAM, on the other hand, the data region is formed by land and groove tracks and is divided into zones, The zones have different numbers of revolutions and different PLL target clock frequencies, respectively. Thus, it is necessary to know which zone is being reproduced/recorded.
Typically, a stepping motor, an encoder, or the like, is used in an optical head traverse drive system of an optical disk recording apparatus. For example, an encoder can be used to implement a system capable of detecting the zone where the light beam is currently located. In such a case, a traverse control may be performed based on a pulse signal from the encoder, while using a pulse signal value for the innermost position of the disk as the initial value.
However, in view of improving the precision and reducing the cost, there is a demand in the art for the use of an inexpensive and simpler DC motor.
When reproducing a DVD-RAM disk with the above-described conventional optical disk apparatus, a single track (either a land or a groove) is identified by a pair of addresses along the opposite sides of the track. If, for example, there is a speck of dust in the address section of the address 210 or if a lens shift occurs to displace the light beam in the direction indicated by an arrow N in FIG. 11, the address 210 may not be properly read when the light beam is scanning along the track 202. In such a case. It is not possible to determine whether the current track is the track 202 or the track 203 based only on the address 201, whereby a data reproduction/recording operation cannot be performed properly.
Moreover, with the conventional optical disk apparatus, the position of the light beam cannot be known immediately after the initialization of the apparatus. The zone where the light beam is currently located is identified only after an address is successfully reproduced by successively switching among the numbers of revolutions and the PLL target frequencies for the respective zones. Thus, such a conventional apparatus has an undesirably long start-up time.
According to one aspect of this invention, an optical disk apparatus includes: a light amount detection section for irradiating an information carrier with a light beam so as to detect information recorded in a data section of the information carrier, wherein the information carrier includes the data section and an address section associated with the data section, the data section is an information track formed by a land or a groove where information can be recorded or reproduced, and the address section contains address information corresponding to the information track which is recorded in the address section by one or more concave or convex pit offset by a predetermined distance from a center of the information track; an address polarity determination section for determining whether the address section over which the light beam has passed is either on an outer periphery side or on an inner periphery side with respect to the center of the information track being scanned by the light beam, based on a signal output from the light amount detection section: an address reproduction section for reproducing the address information recorded in the address section based on a signal output from the light amount detection section: and an address confirmation section for confirming the data section from which or to which data is to be reproduced or recorded, based on the determination result from the address polarity determination section and the address information reproduced by the address reproduction section.
In one embodiment of the invention, the address section includes two or more address regions where the address information is recorded. The address regions are wobbled by a predetermined distance about the center of the information track. The address region is shared by a pair of adjacent information tracks.
According to another aspect of this invention, an optical disk apparatus includes: a light amount detection section for irradiating an information carrier with a light beam so as to detect information recorded in a data section of the information carrier, wherein the information carrier includes the data section and an address section associated with the data section, the data section is an information track formed by a land or a groove where information can be recorded or reproduced, and the address section contains address information corresponding to the information track which is recorded in the address section by one or more concave or convex pit offset by a predetermined distance from a center of the information track; an address section detection section for detecting that the light beam is on the address section based on an output from the light amount detection section; a pulse interval measurement section for measuring an interval between the address sections based on an output from the address section detection section; a radial position estimate section for estimating a radial position of the light beam based on the measurement result from the pulse interval measurement section; and a clock generation section for generating a reproduction clock based on the radial position of the light beam estimated by the radial position estimate section.
In one embodiment of the invention, the optical disk apparatus further includes a tracking error detection section for detecting an amount of tracking error of the light beam passing over the address section. The address section detection section includes a digitization section for digitizing an output from the tracking error detection section. The pulse interval measurement section measures the interval between pulses output from the digitization section. The radial position estimate section estimates the radial position of the light beam based on a time required for one revolution of the information carrier and an output from the pulse interval measurement section.
In one embodiment of the invention, the optical disk apparatus further includes: a tracking error detection section for detecting an amount of tracking error of the light beam passing over the address section; a maximum value measurement section for measuring a maximum value of an output signal from the tracking error detection section for a predetermined period of time; and a minimum value measurement section for measuring a minimum value of the output signal from the tracking error detection section for a predetermined period of time. The address section detection section further includes: a digitization section for digitizing the output from the tracking error detection section; and a threshold value setting section for setting a threshold value which is used when digitizing the output from the tracking error detection section, the threshold value being obtained based on the maximum value and the minimum value.
In one embodiment of the invention, the optical disk apparatus further includes: a tracking error detection section for detecting an amount of tracking error of the light beam passing over the address section: a maximum value measurement section for measuring a maximum value of an output signal from the tracking error detection section for a predetermined period of time; a minimum value measurement section for measuring a minimum value of the output signal from the tracking error detection section for a predetermined period of time; and an average value measurement section for measuring an average value of the output signal from the tracking error detection section for a predetermined period of time. The address section detection section further includes: a digitization section for digitizing the output from the tracking error detection section; and a threshold value setting section for setting a threshold value which is used when digitizing the output from the tracking error detection section, the threshold value being obtained based on the maximum value and the average value or based on the minimum value and the average value.
In one embodiment of the invention, the optical disk apparatus further includes: a tracking error detection section for detecting an amount of tracking error of the light beam passing over the address section: a maximum value measurement section for measuring a maximum value of an output signal from the tracking error detection section for a predetermined period of time; and an amplitude absolute value conversion section for obtaining an absolute value of an amplitude of the output signal from the tracking error detection section. The address section detection section further includes: a digitization section for digitizing the output from the tracking error detection section; and a threshold value setting section for setting a threshold value-which is used when digitizing the output from the tracking error detection section, the threshold value being obtained based on the maximum value and the average value.
In one embodiment of the invention, the pulse interval measurement section measures the interval between the pulses output from the digitization section while ignoring a latter one of pulses which are successively output within a period of time which is shorter than a predetermined period of time.
In one embodiment of the invention, the optical disk apparatus further includes: a tracking control section for controlling the light beam so that the light beam scans along the information track on the information carrier; and an abnormal track jump detection section for detecting that the light beam is scanning off the track. The optical disk apparatus inactivates the pulse interval measurement section based on the detection result from the abnormal track jump detection section.
In one embodiment of the invention, the optical disk apparatus further includes a focusing control section for controlling the light beam so that the light beam is focused on the information carrier in a predetermined focused state. The optical disk apparatus inactivates the pulse interval measurement section when the focused state of the light beam on the information carrier is substantially different from the predetermined focused state or when the focusing control section is inactive.
According to still another aspect of this invention, an optical disk apparatus includes: a light amount detection section for irradiating an information carrier with a light beam so as to detect information recorded in a data Section of the information carrier, wherein the information carrier includes the data section and an address section associated with the data section, the data section is an information track formed by a land or a groove where information can be recorded or reproduced, and the address section contains address information corresponding to the information track which is recorded in the address section by one or more concave or convex pit offset by a predetermined distance from a center of the information track; an address section detection section for detecting that the light beam is on the address section based on an output from the light amount detection section; a pulse counter section for counting the number of signals which are output from the address section detection section within a predetermined period of time; a radial position estimate section for estimating a radial position of the light beam with respect to the information carrier, based on an output from the pulse counter section; and a clock setting section for activating the radial position estimate section when the address information cannot be reproduced and setting a reproduction clock based on the estimated radial position of the light beam.
In one embodiment of the invention, the optical disk apparatus further includes a tracking error detection section for detecting an amount of tracking error of the light beam passing over the address section. The address section detection section further includes a digitization section for digitizing an output from the tracking error detection section. The pulse counter section counts the number of digitized pulses output from the digitization section. The radial position estimate section estimates the radial position of the light beam based on a time required for one revolution of the information carrier and an output from the pulse counter section.
In one embodiment of the invention, the optical disk apparatus further includes: a focusing control section for controlling the light beam so that the light beam is focused on the information carrier in a predetermined focused state; and a control state determination section for determining whether the focusing control section is properly operating. The optical disk apparatus ignores an output from the pulse counter section based on the determination result from the control state determination.
In one embodiment of the invention, the light amount detection section detects the information recorded on the information track based on the light beam having been reflected by the information carrier.
In one embodiment of the invention, the light amount detection section detects the information recorded on the information track based on the light beam having passed through the information carrier.
Thus, the invention described herein makes possible the advantages of (1) providing an optical disk apparatus with which it is possible to identify a predetermined track and to reproduce/record data from/to the track even if one of a pair of addresses cannot be reproduced because of a speck of dust in the address section or a lens shift; (2) providing an optical disk apparatus with which the first address after a start-up or a restart of the apparatus can be reproduced within a reduced amount of time by estimating a current position (zone) of the light beam upon the start-up or the restart; and (3) providing an optical disk apparatus which is inexpensive to implement and can be reliably used with an optical disk which is divided into zones.
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.